Gilled pipes for heat exchange



March 25, 1969 E. PIGNAL 3,434,533

GILLED PIPES FOR HEAT EXCHANGE Filed Nov. 9, 1966 F IG] (PRIOR ART) United States Patent 01 Bee US. Cl. 165-183 2 Claims ABSTRACT OF THE DISCLOSURE In order to increase the heat exchange coefficient and the mechanical strength characteristics of heat exchangers, the invention provides gills or fins that have corrugated legs and an integral foot portion including at least two parallel and axially extending and outwardly protruding ribs adapted to be welded to the surface of the heat exchange tube.

This invention relates to tubular heat exchangers of the gilled type and, more particularly, concerns a novel gill structure for substantially increasing the heat exchange coefiicient of the gilled pipes.

It is well known in the prior art to affix radially extending gills to heat exchange pipes. These gills may be radial, axially spaced individual crowns, helically wound continuous strips, or radial, axially extending and circumferentially spaced ribs.

This invention pertains to a novel gill structure particularly adapted for tubular heat exchangers having gillS in the form of a plurality of radially offstanding, longitudinally extending and circumferentially spaced strips. Any cross-section along the axis of such heat exchange pipes has a star-like appearance. Heretofore, gills of this type have been made of flat strips of U or L cross-section and welded to the tube by means of a weld of relatively small sectional area.

Briefly stated, the invention provides gills of U or L cross-section that are corrugated and which, at their foot portion, have at least two adjacent rib-like protrusions adapted to be welded to the heat exchange tube. It was found that heat exchange structures of this construction have remarkably superior heat exchange characteristics and substantially improved mechanical strength.

The invention will be better understood and further advantages will become more apparent with reference to the ensuing detailed specification taken in conjunction with the drawing, wherein:

FIG. 1 is a fragmentary cross-section of a gilled tube representing the prior art;

FIG. 2 is a perspective view of a novel gill according to the invention;

FIG. 3 is a fragmentary cross-section of a heat exchange tube provided with the novel gills shown in FIG. 2; and

FIG. 4 is a perspective view of another embodiment according to the invention.

In FIG. 1, representing the prior art, there is shown in fragmentary section a heat exchange pipe 1 to which there is welded a fiat, planar gill of U cross-section comprising two spaced, substantially radially offstanding legs 2 and an interconnecting foot portion afiixed to the outer face of tube 1 by means of a longitudinally, axially extending weld 3.

The gill structure of the invention now to be described results in a heat exchange coefficient remarkably superior to that of the structure shown in FIG. 1.

Turning now to FIG. 2, there is shown in perspective a novel gill comprising a pair of substantially parallel,

3,434,533 Patented Mar. 25, 1969 spaced legs 4-4, defining the height of the gill, interconnected by an integral foot portion 5. Legs 4 are corrugated, preferably in such a manner that the corrugations extend parallel to one another and along the length dimension of the gill. Immediately adjacent the foot portion 5 each leg 4 has a relatively short, planar portion before the corrugations begin. Preferably, the corrugations are symmetrical with respect to a plane in which said planar portion lies. The foot portion 5 is provided with a pair of parallel, lengthwise extending and outwardly protruding ribs 6.

FIG. 3 shows, in fragmentary section, a heat exchange tube or conduit 7, to the outer face of which there is aflixed a plurality of gills of the structure shown in FIG. 2. These gills, having corrugated legs 8, extend parallel to the longitudinal axis of tube 7 and are arranged in a parallel, circumferentially spaced relation with respect to one another. It is preferred that said corrugations are symmetrical with respect to a plane containing the longitudinal axis of tube 7. Each gill is afiixed to tube 7 by means of a pair of longitudinal, continuous welds along the peak of ribs 6. Compared with the structure depicted in FIG. 1, each gill of the type shown in FIGS. 2 and 3 has a surface for contacting the ambient fluid medium of about larger without increasing the overall radial dimension of the gilled heat exchange tube. Further, the area of direct contact between each gill and the surface of the tube has been doubled by the provision of contacting ribs 6.

Turning now to FIG. 4, there is shown a second embodiment of the gill according to the invention. Here, the gill shown in perspective has an L cross-section and comprises a corrugated leg 10 and an integral foot portion 11 extending substantially normal to leg 10. The foot portion 11 is provided with a pair of parallel, lengthwise extending and outwardly protruding ribs 9. These gills are arranged on the surface of a heat exchange tube in a manner similar to that described in connection with the embodiment of FIG. 2.

Due to the particular, non-planar profile of the gills constructed according to the invention, adjacent gills on parallel and closely spaced tubes cannot be contiguous so as to block a transversal passage of the ambient fiuid. Thus, it is possible to construct effective heat exchange assemblies of more closely spaced tubes than was possible with planar gill structures used heretofore.

In addition to the improved heat exchange characteristics th novel gill structure also has improved mechanical strength. The double weld ensures a more stable securing means without increase in the thickness of the material and the corrugated nature of the radially olfstanding legs makes them less vulnerable to deformations or other mechanical damage during storage, transportation, installation or other handling operation.

Although two embodiments of the invention have been depicted and described, it will be apparent that these embodiments are illustrative in nature and that a number of modifications in the apparatus and variations in its end use may be effected without departing from the spirit or scope of the invention as defined in the ap ended claims.

What is claimed it: 1. A heat exchanger comprising: (a) a tubular conduit having an external face, and (b) a plurality of circumferentially spaced gills secured to said external face and disposed thereon parallel with the longitudinal axis of said conduit, said gills being axially elongated and each including (1) an axially continuous foot portion extending throughout the length of said gill and disposed substantially parallel with and adjacent 3 9 said external face, said foot portion having at least two axially extending ribs projecting towards said external face and secured thereto by means of a Weld, and (2) at least one leg integral with said foot portion and extending substantially normal thereto, said leg provided with a plurality of radially spaced corrugations extending axially throughout the length of said gill, said corrugations being symmetrical with a plane containing said axis and passing through said leg.

2. An elongated gill adapted to be afiixed to the surface of a heat exchange conduit comprising a foot portion extending throughout the length of said gill and adapted to be disposed immediately adjacent and parallel with the surface and at least one corrugated leg integral with said foot portion and including a relatively short planar portion immediately adjacent said foot portion and extending substantially normal thereto, the corrugations of said leg being symmetrical with respect to a plane lying in said short planar portion.

References Cited UNITED STATES PATENTS 833,486 10/1906 Sager 165-183 851,978 4/1907 Bigsby et al. 165-183 1,321,030 9/1931 Sprong 165183 3,305,013 2/1967 Friedl etal. 1165-183 ROBERT A. OLEARY, Primary Examiner.

THEOPHIL W. STREULE, Assistant Examiner.

P0405) UNITED STATES PATENT OFFICE 569) CERTIFICATE OF CORRECTION Patent No. 533 Dated March 25, 1969 Inventor(s) Edmond Pignal It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

F- In the heading, "assignor to Biraghi (Societe Anonyme) should read --assignor to Societe des Fabrications BIRAGHI- amnspose 4 F SIGNED AND 1 swan MAR 101970 Edward M. Fletcher, Jr.

Commissioner of Patents 

